[David Ellis]

Bill,

I have a question regarding slow turn-on circuitry for Jolida tube amps.  Er, is there any time-delay for the cathode to annode potential voltage across any of the tubes in the Jolida tube amps?  I checked the schematic for my 302b and didn't see anything.  It appears the potential is very present across the unheated grid immediately when the 302b is turned "on".

My 302b is doing well, but I did loose a Svetlana El34 after about 1 year.  My Amperex driver 12AX7s and 12AT7s are doing fine.

In this regard, do you have any backround with the expected change in lifespan for a tubes in amps with/without votage potential delay circuitry?  

Thanks,

[Bill Baker]

Greetings David,

Er, is there any time-delay for the cathode to annode potential voltage across any of the tubes in the Jolida tube amps? I checked the schematic for my 302b and didn't see anything. It appears the potential is very present across the unheated grid immediately when the 302b is turned "on".

  There is no delay in the circuitry for the Jolida tube amplifiers. I do have a circuit design for a soft start/delay but have not yet had the time to experiment or install it into one of the amps.

My 302b is doing well, but I did loose a Svetlana El34 after about 1 year. My Amperex driver 12AX7s and 12AT7s are doing fine.

In this regard, do you have any backround with the expected change in lifespan for a tubes in amps with/without votage potential delay circuitry?

  I personally ran a stock 302B for about 18 months with the same set of output tubes (Svetlana EL34s) before changing tubes just to try something different. This amp was used almost on a daily basis as it was connected to my TV in my home with the internal TV speakers turned off so ithad to be on anytime you wanted to watch TV.

 I have had customers run the same set of output tubes for almost 3 years without fail in both the 302 and 502 (same circuitry).

  I would say much of this has to do with the quality of the tube as much as the circuitry of the amp. It is my guess that you can easily get 3-5 years out of output tubes in a Jolida amp.

[David Ellis]

3-5 years does seem about right.  I thought my 1 yr on the Svetlana El34s was a little quick. Then, only 1 of the tubes died.  It might have been a bad tube.

I apprecaite your insight and expertise!

Dave

[Bill Baker]

HI Dave,
  The big broblem I have run into lately has been the production quality of tubes. I have found the best current production tubes, both build and sonic quality, to be the SED tubes. Another reliable tube is the Sovtek.
  These are not quite the same as the older Svetlana units as they have much better quality control and the sonic differences between these and the regular Svetlana labeled tubes is very noticable.

  The tubes I have had the most problems with in a variety of components are the Svetlana and Electro Harmonix. I have received orders of these tubes where 2 out of every 10 tubes went out within 3 months.

  In my opinion, you are doing very well getting even a year from Svetlana EL34 tubes

 It is for this reason I now stock only the Sovtek 6550 for use in testing my amps (including the modified ASL Hurricanes & Monsoons) and supply them with all my custom built amps. I still stock the Svetlana EL34 but at the volume of tubes I buy, it is worth it for me if I have to replace a customer's tube within the warranty period I offer. I may switch my EL34's over to Sovtek also but I prefer the sound of the Svetlana EL34 over the Sovtek.

  I do not stock expensive tubes as everyone has their own personal taste and preferences and I am not into retail sales of tubes. That would be an additional set of headaches.

  What's one to do?

[David Ellis]

Your response is very thorough.  I did indeed have the SED - "C" labeled tubes.  I thought that I might have been alone in my tube death, but it appears that all is normal.  I certainly understood there would be some puttering involved when using a tube amp.  This is perfectly acceptable.

I did learn that thetubestore.com labeled my old tubes with a number indicating the bias current - or something like that.  Anyhow, I guess this number should provide a fairly close match for replacement tubes.  This is pretty neat, and a great idea by thetubestore.com .  I ordered some new SED tubes and will pull the OEM tubes when the new SEDs arrive.

Thanks again for all your help and dedication to this hobby!

[macmeech]

David-

Are you satisfied with the dynamics of your speakers driven by the Jolida? I have had opportunity to compare Sovteks on the left channel with EHs on the right channel. In the case of EL84s, the ElectroHarmonix(s) are definitely more transparent. The failure rate has been 1/4, but we think that was a stuck bias screw.

[Bill Baker]

I did learn that thetubestore.com labeled my old tubes with a number indicating the bias current - or something like that. Anyhow, I guess this number should provide a fairly close match for replacement tubes. This is pretty neat, and a great idea by thetubestore.com . I ordered some new SED tubes and will pull the OEM tubes when the new SEDs arrive.

 I agree David, thetubestore provides a very good service with their "perfect pairs" (their Stereophile ads aren't bad either ).
Many of my customers now go through the tube store for their exceptional service. Very good people to work with.

[David Ellis]

Are you satisfied with the dynamics of your speakers driven by the Jolida?

Yep, sure, you betcha'.  No problems here.  The dynamics are great.  

On a SPL level things are decent too.  The 302b runs out of gas about the same time the 1801s run out of gas.   The 1801s will handle just a sosh more juice than the 302b will supply, but this margin is very close.  This is quite loud, but obviously not rock-concert loud.  I have blown a few fuses in the 302b when pushing the limit, but have learned the threshold.  

[macmeech]

Are you satisfied with the dynamics of your speakers driven by the Jolida?

Yep, sure, you betcha'.  No problems here.  The dynamics are great.  

On a SPL level things are decent too.  The 302b runs out of gas about the same time the 1801s run out of gas.   The 1801s will handle just a sosh more juice than the 302b will supply, but this margin is very close.  This is quite loud, but obviously not rock-concert loud.  I have blown a few fuses in the 302b when pushing the limit, but have learned the threshold.  

You are truly the original mad scientist.  Now back to your cell to make speaker cabinets!